Tampering with products is an escalating and serious problem which may result in serious harm and even death to the unwary consumer. Most of the protective methods available today can be easily circumvented by the tampering sophisticate. Unfortunately, protective labels can be soaked off of a container using water, the container opened, harmful substances added, and the protective label reattached without clearly indicating that tampering has occurred.
A well-accepted method for providing limited protection against container tampering employs a perforated label structure which, when removed from a container, fragments and disintegrates, such as the label disclosed by U.S. Pat. No. 5,013,088 (Marin, 7 May 1991). Another popular design, as described in U.S. Pat. No. 4,652,473 (Han, 24 Mar. 1987), utilizes a multiple layer amorphous polymer construction which delaminates when the label is removed from a surface to which it is adhered. These designs, however, fail to indicate that tampering by means of water immersion has occurred. A label, used in blind clinical studies, that reacts with water by dissolving a rice paper layer and exposing underlying medical information, is disclosed by U.S. Pat. No. 3,740,081 (Whipperman, 19 Jun. 1973). This label is employed to preserve the privacy of the underlying medical information, rather than protecting containers from illicit tampering. Designs similar to those disclosed by Marin and Han have an additional disadvantage in that, given sufficient skill and patience, the protective label can be reapplied to the container after the tampering act is accomplished, thus providing a false indication of the integrity of the product.
Therefore, there is a need for a sophisticated tamper-evident label that will clearly indicate to the consumer that tampering of the container has occurred.
Accordingly, one object of the present invention is to clearly communicate to the consumer that tampering of the label by means of water immersion has occurred.